Angiotensin II is the primary hormone active in the renin-angiotensin system and elicits effects on the regulation of arterial pressure, volume homeostasis and hypertension. Activation of the renin-angiotensin cascade begins with renin secretion from the juxtaglomerular apparatus of the kidney and culminates in the formation of angiotensin II, the primary active species of this system. Angiotensin II is an octapeptide which is a potent vasoconstrictor and also promotes aldosterone secretion, promotes sodium and fluid retention, inhibits renin secretion and increases vasopressin secretion.
Previous studies have shown that antagonizing angiotensin II at the receptor level is a viable approach to controlling the renin-angiotensin system. There are several known angiotensin II antagonists, many of which are peptidic in nature. Such peptidic compounds are of limited use due to their lack of oral bioavailability or their short duration of action. Also, commercially-available peptidic angiotensin II antagonists (e.g., Saralasin) have a significant residual agonist activity which further limits their therapeutic application.
Non-peptidic compounds with angiotensin II antagonist properties are known. For example, the sodium salt of 2-n-butyl-4-chloro-1-(2-chlorobenzyl)imidazole-5-acetic acid has specific competitive angiotensin II antagonist activity as shown in a series of binding experiments, functional assays and in vivo tests [P. C. Wong et al, J. Pharmacol. Ext. Ther., 247(1), 1-7 (1988)]. Also, the sodium salt of 2-butyl-4-chloro-1-(2-nitrobenzyl)imidazole-5-acetic acid has specific competitive angiotensin II antagonist activity as shown in a series of binding experiments, functional assays and in vivo tests [A. T. Chiu et al, European J. Pharmacol., 157, 13-21 (1988)]. A family of 1-benzylimidazole-5-acetate derivatives has been shown to have competitive angiotensin II antagonist properties [A. T. Chiu et al, J. Pharmacol. Exp. Ther., 250(3), 867-874 (1989)]. U.S. Pat. No. 4,816,463 to Blankey et al describes a family of 4,5,6,7-tetrahydro-1H-imidazo(a,5-c)-tetrahydro-pyridine derivatives useful as antihypertensives, some of which are reported to antagonize the binding of labeled angiotensin II to a rat adrenal receptor preparation and thus cause a significant decrease in mean arterial blood pressure in conscious hypertensive rats. EP No. 253,310, published 20 Jan. 1988, describes a series of aralkyl imidazole compounds, including in particular a family of biphenylmethyl substituted imidazoles, as antagonists to the angiotensin II receptor. EP No. 323,841 published 12 Jul. 1989 describes four classes of angiotensin II antagonists, namely, biphenylmethylpyrroles, biphenylmethylpyrazoles, biphenylmethyl-1,2,3-triazoles and biphenylmethyl 4-substituted-4H-1,2,4-triazoles, including the compound 3,5-dibutyl-4-[(2'-carboxybiphenyl-4-yl)methyl]-4H-1,2,4-triazole. U.S. Pat. No. 4,880,804 to Carini et al describes a family of biphenylmethylbenzimidazole compounds as angiotensin II receptor blockers for use in treatment of hypertension and congestive heart failure.
There are several families of 1,2,4-triazole compounds having substituents attached to the nitrogen atom at the one-position of the 1H-triazole. For example, U.S. Pat. No. 4,118,487 to Regel et al describes a family of azol-1-yl-methane compounds for use as antimycotic and antibacterial agents including, specifically, the compound (1-biphenyl-4-yl-1-phenyl)methyl-1H-1,2,4-triazole. U.S. Pat. No. 4,381,306 to Regel et al describes a family of hydroxypropyl-triazole compounds for use as antimycotic agents including, specifically, the compound (1,2,4-triazol-1-yl)methyl-4-chlorobenzyl-biphenyl-4-yl-carbinol. U.S. Pat. No. 4,480,114 to Regel describes a family of 2-(4-biphenyl)-2-(halophenyl)-oxirane compounds having antimycotic activity including, specifically, the compound (1,2,4-triazol-1-yl)methyl-4-chlorophenyl-4-chlorobiphenyl-4-yl-carbinol.
However, not much is known about the conformations and interactions of these non-peptide antagonists with the vascular angiotensin II receptors. It has been established in the literature that there are distinct angiotensin II receptor subtypes with differing functions [A. T. Chiu et al, Biochem. Biophys. Res. Comm., 165, 196-203 (1989)]. The receptor subtypes affecting vascular constriction is believed to be an important target for the treatment of hypertension [P. C. Wong et al, J. Pharmacol. Exp. Ther., 255, 584-592 (1990)]. Compounds which conformationally restrict the possible orientations of the pharmacophores incorporated therein may maximize the interaction between those pharmacophores and the binding site of the receptor subtype or subtypes of interest. Therefore, conformationally restricted angiotensin II antagonists may increase the selectivity to the specific receptor subtype of interest, thereby reducing possible side effects associated with binding to the other receptor subtypes not involved in the hypertension pathway.
There are several families of conformationally restricted angiotensin II antagonists reported in the literature. For example, tricyclic benzoxazepines [A. P. Thomas et al, J. Med. Chem., 35, 877-885 (1992)] were used to potentially lock in a phenyl group in an energetically favorable conformation. Conformationally restricted imidazoles having a biphenyl radical substituted with bulky side groups to sterically limit the rotation of the phenyl groups and form a more rigid spatial relationship were described in P. R. Bovy et al, J. Med. Chem., 34, 2410-2414 (1991). These previous attempts to lock the conformation of angiotensin II antagonists do not stabilize conformations axial to a heterocyclic ring by means of orthogonally attaching a substituted biphenyl radical to a non-aromatic bridging ring.